It is a classic action movie scenario. Our hero, burdened with disarming the doomsday weapon, killing the bad guy, saving the love interest – or all three at once – must assault a building packed to the brim with armed goons. Thankfully, being the protagonist, our hero is also blessed with bottomless magazines and unfailing aim, and proceeds to simply charge into the building guns blazing. Without fail, every bullet finds its mark, sending legions of goons crumpling to the ground dead or – if it’s that kind of movie – flying across the room like rag dolls, their lifeless bodies smashing through walls and plate-glass windows for maximum cinematic mayhem. While most of us are aware that this is not how a real-life gunfight would go down, just how removed from reality is this scene? Well, while it can easily be proven that no regular man-portable firearm can send a body flying across the room, in most cases people will indeed crumple to the ground when shot. The reason for this might seem rather obvious, except for one puzzling fact: regardless of where the bullets hit or whether said hits are immediately fatal, most people will still drop. Stranger still, scientists still aren’t quite sure why. Welcome to one of the more surprising scientific mysteries of our modern age: why to people drop when shot?

First off, let’s tackle the myth that a gunshot will send you flying across the room as if you’ve just been hit by a speeding freight train. The main reason this is impossible has to do with energy transfer. Most bullets are relatively small in diameter – usually less than one centimetre – and travel at extremely high speeds – for example, 352 metres per second for a 9mm Parabellum handgun bullet and 954 metres per second for a 5.56mm NATO rifle bullet. This means that on impact, a tremendous amount of force is concentrated over a tiny cross-sectional area, allowing most bullets to easily slice through human flesh without transferring much of their energy to the victim’s body. But even in cases where the bullet stops dead – such as when it impacts a particularly dense bone or a bulletproof vest – being so light, most bullets don’t have nearly enough momentum to send a person flying across the room. To use an extreme example, let’s imagine firing the massive .50 BMG round used in the M2 heavy machine gun and Barrett M82 anti-materiel rifle at a person holding an armour plate, such that the bullet is stopped dead by the plate and transfers all its energy to our hapless target. In such an inelastic collision, momentum – defined as mass times velocity – is conserved, meaning that after the collision, the combination of projectile and target will have the same momentum as they did before the collision. The .50 BMG bullet has a mass of 42 grams and a muzzle velocity of 928 metres per second, meaning it has a momentum of 38.9 kilogram-metres per second. Dividing this momentum by the mass of the target – 98.9 kilograms for the average American male – yields a rearward velocity of 0.39 metres per second, meaning that in a frictionless environment – say, wearing ice skates on a rink – the impact would propel our unfortunate cannon fodder rearward at a leisurely 1.4 kilometres per hour. Standing on solid ground, such an impact could certainly knock a person to the ground, but would be nowhere near powerful enough to fling them across the room. Indeed, this film trope is easily debunked by the fact that firearms are usable at all. According to Newton’s Third Law of Motion, for every action there is an equal and opposite reaction, meaning that if a bullet really could send its victim flying across the room, the shooter would also be blown rearward with equal force by the recoil of the firearm. And if somehow all this theory still isn’t enough to convince you that people getting blown across rooms is pure Hollywood ballyhoo, in a February 6, 2005 episode of the television series Mythbusters, this myth was physically tested by shooting various firearms at a dummy made of ballistics gel. In all cases, it was found that no practical handheld firearm produced enough muzzle energy to knock the dummy back more than a few inches. Achieving the classic Hollywood effect would require something on the order of a small artillery piece, at which point you will no longer be blowing someone across the room so much as using their insides to redecorate the walls…

But anyway, back to the mystery at hand. While the obvious answer to the question “Why do people drop when shot?” is “Duh, Simon: because they’ve been shot!” in reality, the physiology of gunshot wounds is far more complicated than it might at first appear. There are relatively few parts of the human body where a bullet impact will produce instantaneous death, these being certain parts of the brain, spinal cord, and heart. But a great many people have survived hits to both organs – for a time, at least – with the cause of death in the vast majority of gunshot cases being exsanguination – AKA blood loss. Yet time and time again in military conflicts or criminal, police, and accidental shootings, people will crumple to the ground when shot in places which are not immediately lethal. Of course, in some cases the person was shot in the legs and simply collapsed due to extreme pain or because their bones were broken and could no longer support their weight, but the same phenomenon is observed in people shot in the chest, abdomen, and arms. Theoretically, such people should be able to carry on walking for some time before passing out from blood loss – especially if their system is full of adrenaline. So, what exactly causes them to drop?

Interestingly, the leading theory as to why people drop when shot holds that the phenomenon is purely psychological, rooted in popular depictions of gun violence. Because people in movies and TV shows drop instantly when shot, when people are shot in real life they, too drop to the ground because that is what is supposed to happen. This theory, posited by American ballistics expert Duncan MacPherson, is supported by the fact that animals, which have no conception of how firearms or gunshot wounds work, react very differently from humans to being shot. As any hunter can attest, a deer shot through the heart can run up to fifty metres before blood loss takes it down. The same holds for humans who have had little exposure to firearms. For example, from 1899 to 1913, the United States Military fought a protracted counterinsurgency in the Philippines against a group of fiercely independent muslim tribesmen known as the Moros. During early battles, American troops were shocked to discover that their .30 calibre Krag-Jørgenson and M1903 Springfield rifles and .38 calibre M1892 revolvers did little to stop the hordes of charging Moros, with multiple shots being needed to take down a single man. As Colonel Louis A. LaGarde of the Army Medical Corps reported in 1905:

“Antonio Caspi, a prisoner on the island of Samar, P.I. attempted escape on Oct. 26, 1905. He was shot four times at close range in a hand-to-hand encounter by a .38 Colt’s revolver loaded with U.S. Army regulation ammunition. He was finally stunned by a blow on the forehead from the butt end of a Springfield carbine.”

On many occasions Moro berserkers, known as juramentados, were able to charge through a hail of bullets and cut down a handful of Americans before finally dying of their wounds. The same phenomenon was encountered by American troops deployed to China in 1900, where they faced equally fanatical – and seemingly bulletproof – anti-colonial rebels known as the Boxers. It is now believed that naïveté regarding the effects of firearms, coupled with adrenaline and religious or nationalistic fervour allowed the Moros and the Boxers to ignore their wounds and keep fighting until physiology took its inevitable toll. The experience of fighting in the Philippines and China convinced the U.S. Military that it needed a harder-hitting pistol cartridge capable of knocking a man down with one shot. Thus, in 1904, Colonel John Thompson, head of the Army Ordnance Department and later inventor of the famous Thompson Submachine gun or “Tommy” gun, conducted a series of tests with Major LaGarde to evaluate the stopping power of various handgun cartridges – and for more on Colonel Thompson and his most famous creation, please check out our previous video The “Chicago Typewriter”: the Story of the Legendary “Tommy Gun”. These tests, conducted at the Union Stockyards in Chicago, involved firing various cartridges at live cattle and horses as well as human cadavers and noting how long the animals took to die or how far back the cadavers were pushed by the bullet impact. The results revealed that hollow-point or “dum-dum” bullets which expand on impact were most effective, but as such projectiles were prohibited in warfare by the 1899 Hague Convention, Thompson and LaGarde recommended that the Army adopt a cartridge no smaller than .45 calibre. This recommendation eventually led to the adoption of the .45 ACP cartridge and the legendary Colt M1911 automatic pistol.

While the “naïveté” theory for why most people drop when shot is by far the most popular, other experts argue that dropping is simply a logical reaction to trauma and danger. Simply put, dropping to the ground allows the victim to guard and tend to their wounds and avoid getting shot at again. Still others, however, reject psychological explanations altogether and instead posit a purely physiological reason for why people drop when shot. For example, Dr. Dennis Tobin, a neurologist at the Citizens Medical Center in Victoria, Texas, theorizes that the common reaction to being shot is due to a structure in the brain known as the Reticular Activating System or RAS. Located in the brainstem, the RAS filters out irrelevant information pouring in from our senses, preventing our brains from becoming overloaded. So if you are able to listen in on a single conversation in a crowd or sleep next to a busy highway, thank your RAS. A gunshot wound typically produces a large amount of pain and other trauma, unleashing a barrage of nerve impulses which can quickly overwhelm the brain. Certain projectiles can even unleash powerful pressure waves which can travel through the body and potentially damage delicate brain structures. This is especially true of small, high-velocity rounds like 5.56mm NATO, which can momentarily create large cavities as they pass through tissue, inflicting significant damage. According to Dr. Tobin, in order to protect the brain from this onslaught, the RAS immediately shuts down all non-essential bodily functions – including maintaining muscle tone. This causes the leg muscles to suddenly weaken and the shooting victim to collapse. This theory is supported by research done in 1988 by A.M. Göransson and in 2004 by a team from the University of Science and Technology in Hefei, China – and any animal lovers in the audience might want to turn off the video right now…

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… because both studies involved shooting live pigs and dogs in the legs with real bullets and measuring the effects on their brains.

Whether psychological, physiological, or a bit of both, the real reason most people drop when shot remains as elusive as ever, largely because most of the data we have on the subject comes from anecdotal military reports or experiments conducted on animals. For rather understandable reasons, people aren’t exactly lining up around the corner to be shot for science – and even if they were, no ethics review board on the planet would approve such an experiment. But whatever the real answer is, I think we can all agree on one thing: it’s probably a good idea to just not get shot.

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